ON A FINE Sunday evening in August 1985, some of the crowd at the Lark By The Lee concert in Cork began to drift away from the Lee Fields at the end of Freddie White’s set.

A woman parked nearby wound down the window of her car and shouted out to a couple of the lads passing her by: “Don’t leave yet, U2 are coming on next.”

She was met with the reply: “They are, yea... and David Bowie is playing as well!”

By the time that young man got home and sat down to watch the nine o’clock news, he would’ve been spluttering his Kimberley biscuit back into his cup of tea. As Charles Mitchel probably reported, U2 did come on next. It was a secret gig in the midst of the Unforgettable Fire tour to thank Cork — which couldn’t be included on the official series of gigs because of logistical issues — for the support the city had given the band in their early days.

The woman in the car, the late Phyl McCarthy, knew about the unpublicised appearance because her husband, Joe, was filming it for RTÉ. They had even brought their son Tony along to watch it from stage-side.

Fast-forward more than 30 years and Tony is getting ready to roll out some of that footage for a new documentary. U2 Agus An Arc airs next Thursday on RTÉ One, two days before the group takes to the stage at Croke Park. It traces the band’s formative connections with Cork in the context of the thriving music scene centred around the Arcadia in the late 1970s and early ’80s.

David Corio’s picture for ’NME’ of Bono on stage at the Arcadia in Cork in 1980.

“It was a great time for music in Cork, and we wanted to tell that story, as well as showing U2’s part in it,” says McCarthy of Forefront Media. As somebody who lived through that post-punk era, McCarthy remembers an exciting time for music in his native city, where bands like U2 would play on bills with local acts, and there would also be visits from British groups like The Specials, The Stranglers, and The Cure.

At the heart of it all was Elvera Butler, a UCC student from Thurles who had the brainwave to bring some of the college’s social events to the city. She set up the Downtown Kampus in an old ballroom near the train station.

Among the other bright sparks in the Irish music business at the time was Paul McGuinness, the ambitious young manager working hard to break his band beyond the national scene.

McGuinness saw that the Arcadia was the perfect place for U2 to showcase their talents. Though Bono and co were well appreciated in their home town, they couldn’t yet pull the crowds of 1,000 or so that would regularly turn up on a Saturday night in Cork. Before the band had even signed to a label, McGuinness managed to persuade the NME, the premiere British music paper of the time, to send over a reporter and photographer. Paul Morley, still a highly respected music and media figure, was quite impressed with what he saw.

“Queues form early, the dance hall fills. Most of these people know an amp from a tea bag,” he subsequently wrote in his NME feature in March 1980. “And because they’ve been given a tantalising series of glimpses of a fuller life, they’re aware and starving.”

Elvera Butler of the Arcadia; documentary maker Tony McCarthy

Morley had interviewed the band in the “cheaply luxurious lounge” of the Country Club Hotel that morning, and the roof of that premises also provided the iconic photograph by David Corio that was to later feature on the cover of the group’s own 2009 book, U2 by U2.

By the time the English duo had witnessed one of the band’s nine gigs at the Arcadia, a speculative buzz had already been getting louder around the band. In fairness to Morley, however, he was one of the first people outside of Ireland to spot their potential.

“The Cork U2 set shows how the group will be received in Britain when they begin to be accepted; excitedly, stupidly,” he wrote.

U2 at the Arc had all the ingredients for something special. A tight and talented band that still had a raw energy about them; and a crowd eager to feed off that buzz as they dissolved into a heaving mass. No capital city coolness to prevent them jumping around. No mobile phones to sap the energy.

In U2 Agus An Arc, Morley fondly recalls that visit to Cork and the already compelling live prowess that would eventually fill stadiums all over the globe. Butler is another of the English-speakers to feature in the mostly Irish and subtitled documentary, but the programme makers also hit on a rich vein of Irish speakers.

We hear accounts as Gaeilge from people such as Giordaí Ua Laoghaire, the innovative Nun Attax guitarist who may have influenced The Edge; Ciarán Ó Tuama, a rare man with a camera who had the foresight to take many great photographs of the era (and whose band Cypress Mine also played that Lark By The Lee gig); and John Spillane, who supported U2 at the Arc with his band Sabre.

“It was a really special time so it’s great to be able to tell the story,” says Tony McCarthy. “And it shouldn’t be forgotten that it really worked both ways for U2 and Cork. As well as picking up many of their best crew members here, U2 took some very important steps on the road to fame when they were in Cork. And in return, we all got some great nights out.”